1. Field of the Invention
The present invention relates to radiant gas burners, and more particularly, to an improved radiant gas burner of the type including a central burner tube surrounded by an annular refractory tile and a method of burning fuel gas and air with low NO.sub.x production.
2. Description of the Prior Art
Radiant burners of the type which include central fuel gas-air mixture burner tubes surrounded by annular refractory tiles are well known and have been utilized in conjunction with reformers, cracking furnaces and the like for many years. The refractory tiles have generally been adapted for insertion into openings in furnace walls, and the burner tubes which extend through central passageways in the burner tiles discharge fuel gas-air mixtures in directions generally parallel and adjacent to the internal faces of the burner tiles. The combustion of the fuel gas-air mixtures causes the faces of the burner tiles to radiate heat, e.g., to process tubes, and undesirable flame impingement on the process tubes is thereby avoided.
Heretofore, the nozzle portions of the burner tubes of radiant burners which extend short distances past the burner tiles have been threadedly connected to the forward portions of the tubes. However, the threaded nozzle connections have been located close to the interior faces of the burner tiles which are exposed to high temperatures, i.e., temperatures in the range of from about 1500.degree. F. to about 2500.degree. F. While such threaded nozzle connections were intended to allow the nozzle portions of the burner tubes to be periodically removed and replaced, because of the high temperatures the metal forming the threads has often fused and prevented the ready removal of the nozzle portions. Consequently, the more recent radiant burners have included burner tubes with the nozzle portions welded thereto. In order to change the nozzle portions of such burner tubes when they deteriorate, it is necessary to dismantle the burner apparatus, cut off the deteriorated nozzle portions and re-weld new nozzle portions thereon. Thus, there is a need for improved radiant gas burners which include readily replaceable burner tubes.
More stringent environmental emission standards are continuously being imposed by governmental authorities which limit the quantities of gaseous pollutants such as oxides of nitrogen (NO.sub.x) and carbon monoxide which can be emitted into the atmosphere. Such standards have led to the development of various improved gas burner designs which lower the production of NO.sub.x and other polluting gases. While radiant gas burners have also been improved whereby combustion gases containing lower levels of pollutants are produced, additional improvement is necessary. Thus, there is also a need for an improved method of burning fuel gas and air using a radiant gas burner whereby combustion gases having lower pollutant levels are produced.